The navigator attribute of the Window interface must return an instance of the Navigator interface, which represents the identity and state of the user agent (the client), and allows Web pages to register themselves as potential protocol and content handlers.

Currently, HTML 5 defines four properties and two methods:

appName

appVersion

platform

userAgent

registerProtocolHandler

registerContentHandler

This is only a subset of navigator properties and methods that browsers already support. See Navigator Object on Google Doctype for complete browser compatibility information.